Circuit breaker operating mechanism



Jan. 15, 1963 D. M. UMPHREY CIRCUIT BREAKER OPERATiNG MECHANISM INVENTOR. Donald (ff. Z/mp/rr'g BY 5 Sheets-Sheet 1 flttarm v Filed April 7, 1961 CIRCUIT BREAKER OPERATING MECHANISM Filed April 7, 1961 3 Sheets-Sheet 2 a) i FY 4 126' a! $g E. 1Q ,az a 20 u! INVENTOR.

Donald ff "P BY Jan; 15, 1963 D. M. UMPHREY 3,073,924

CIRCUIT BREAKER OPERATING MECHANISM Filed April 7, 1961 3 Shuts-Sheet 3 IN VEN TOR.

Donald M 01/30/221 BY fltzarng/ United States atent @fiice 3,073,924 Patented Jan. 15, 1963 3,073,924 CHKCUIT BREAKER OPERATING MEQHANESM Donald M. Umphrey, Palo Alto, Calif assignor to McGraw-Edison Company, Milwaukee, Wis, a corporation of Delaware Filed Apr. 7, 1961, der. No. M31577 14 Claims. (Cl. 200-82) This invention relates to circuit breakers and, more particularly, to hydraulic circuit breaker operating mechanisms.

The class of circuit breaker operating mechanisms in which the instant invention falls, is that wherein a hydraulic piston is operable to move the circuit breaker contacts to their closed position whereupon they are mechanically latched. In the particular type of device to which the instant invention is applicable, the piston is separated from the high pressure supply by a hydraulically operated relay valve which is controlled by an externally actuable pilot valve. Trip-free operation is achieved by means of a valve actuable upon the receipt of an opening signal to cause the hydraulic piston to be vented to the ambient so that the partially closed device may be instantly reopened.

it is an object of the invention to provide a hydraulically operable circuit breaker having an externally actuable pilot valve which initiates a hydraulic closing operation, with valve means operable to produce trip-free operation regardless of the position of the pilot valve. Another object is to provide such circuit breakers with a normally latched trip-free valve which will not relatch when the pilot valve is open. A further object of the invention is, to provide a trip-free valve which will immediately relatch after an opening operation if the pilot valve has recloscd in preparation for fast reclosure of the circuit breaker but which will not relatch if the pilot valve remains open. Another object of the invention is to provide such a trip-free valve which prevents reclosure of the circuit breaker should the pilot valve remain open after a trip-free operation.

It is yet another object of the invention to provide in a hydraulic circuit breaker operating mechanism, means for promptly removing operating piston-pressure at the end of the switch closing operation but which allows sutiicient movement of the operating mechanism to insure engagement of the contact latch. A further object of the invention is to provide such actuating piston pressure removing means which is operable by the piston itself but which does not require overtravel thereof.

These and other objects and advantages of the instant invention will become more apparent from a detailed description of the preferred embodiment thereof taken with the accompanying drawings in which:

FIG. 1 is a schematic representation of the hydraulic control mechanism according to the instant invention;

FIG. 2 is a sectional view of a portion of the hydraulic circuit breaker control according to a preferred embodiment of the instant invention; and

FIG. 3 is a view taken along lines 33 of FIG. 2.

According to one of its aspects, the invention comprises a circuit breaker having main contacts, contact opening means, hydraulically operable means for closing the contacts, a source of hydraulic pressure, pilot means biased toward an initial position and operable when in a final position to effect the connection of the operating means to the source so that a closing operation will be initiated and actuating means for initiating the movement of the pilot means toward its final position. The source ressure is normally eliective to hold the pilot means in its final position after movement thereto following the operation of the actuating means. The hydraulically operable means is effective when the main contacts reach their fully closed position to render the pressure source ineffective to hold the pilot means in its final position so that it will be returned to its initial position. In the preferred embodiment of the invention the pilot means has a pair of opposed pressure areas. When the pilot means is in its final position one area is subject to the pressure source and the other is vented to the ambient through the operating means. When the operating means reaches its contacts closed position, the other area is isolated from the ambient so that the pressure on the opposed areas can equalize through a restricted passage. This allows a biasing spring to return the pilot means to its initial position.

According to another of its aspects, the invention includes a pressure responsive relay valve for connecting the operating means to the source whereby the contacts are closed, a pressure responsive trip-free valve and a selectively operable pilot valve for effecting the connection of the pressure responsive relay valve and trip-free valve to. the source to initiate a contact closing operation. The pressure responsive trip-free valve is normally latched against the source pressure but upon being released is movable to an open position to ellect the venting of the operating means. Biasing means urges the trip-free valve toward its closed position but is normally inefiective to relatch the same against system pressure when the pilot valve is open. A normally open auxiliary valve is operable to isolate the pressure responsive relay valve from the source when the pilot valve remains open following a trip-free operation. In this manner, the trip-free valve means is prevented from relatching and an unintended reclosure of the device prevented if the pilot valve should remain open following a trip-free operation.

Referring now to the drawings in greater detail, the hydraulically operated circuit breaker is shoWn schematically in FIG. 1 to include main interrupting contacts it) which are coupled by a linkage mechanism 12 to an opening spring 14 which urges the interrupting contacts it) toward their open position. Such movement of the interrupting contacts lid is normally prevented by a latch assembly to. Tripping of the latch assembly 16 to release the interrupting contacts ltl for movement toward their open position is accomplished by an externally actuable latch release solenoid 17. A hydraulic control mechanism 18, for providing trip-free reclosure of the interrupting contacts it) and for recharging the opening spring 14, is housed in a metallic block 20 which in conjunction with a metallic housing 22 provides a sump 23 for receiving the hydraulic operating fluid, such as oil. In addition, the housing 22 also encloses a high pressure hydraulic source 24 for driving the control mechanism 18. A maintenance valve 25 is operable to separate the hydraulic control assembly 18 from the high pressure source 24 so that the circuit breakers main interrupting contacts 10 may be operated independently of the control assembly.

The main interrupting contacts 19, which are shown in their closed position in. FIG. 1, include a conductive bridging bar 30 carried on the lower end of an insulating link 31 and which is movable therewith into and out of engagement with a pair of fixed contact members 32 to complete a series circuit between external terminals (not shown) which connect the circuit breaker to the system being protected.

The linkage mechanism 12 includes a triangularly shaped element 34 which is pivotally mounted at one corner on a fixed shaft 35. The other corners of element 34 are pivotally connected at 36 to a stem 38 rigidly extending from the opening spring assembly 14 and at 39 to a link 44 extending from the hydraulic control assembly 18. The linkage mechanism 12 also includes a coupling link 43 pivotally connected at one end to point 36 and at its other end 41 to a bell crank 42 which is pivotable about a fixed shaft 44. The other end of crank 4-2 is connected at 45 to a linkage 46 for converting the arcuate motion of point 45 to straight line motion of the link 31. This converting linkage 46 includes a first member 48 pivotally connected at one end to the upper end of the insulating link 31 and at its other end to a second element as which swivels on a fixed shaft 56.

The latch assembly 16 includes a latch arm 52 which is pivotally mounted at $3 on the block 26 and which is urged for rotation in a clockwise direction by a reset spring 54. The assembly 16 also includes a latch crank 55 which is connected at one end by a link 56 to the hydraulic control assembly 13 and which is urged by said assembly as well as opening spring 14, as will be more fully described in detail hereinbelow, for clockwise rotation about a fixed pivot pin 58 and against the action of a reset spring 59. Such rotation, however, is normally prevented by a latch tip 64, on the latch arm 52 which engages the latch crank 55 adjacent its connection with link 56.

The latch assembly 16 also includes a latch toggle assembly 62 coupled to the latch crank 55 through the agency of a link 63 which pivotally engages the end 64 of latch crank 55 opposite the latch tip 6d. The latch toggle assembly 62 comprises a first element 65 pivotally mounted around a fixed pin 66 and a second element 67 which is connected to the first element 65 by a knee pin 68 which also forms the connection of the toggle assembly 62 with the link 63. A sear spring 69, surrounding the knee pin 68 and engaging the fixed pin 66 and a pin 76 carried by the element 67, urges element 67 against a fixed stop 71 and its tip into latching engagement with a notch 72 formed in a long vertical link 74 which is connected to the hydraulic operating mechanism 18 at its lower end and which is pivotally connected at 76 to the link 469. 7

From the discussion thus far, it will be appreciated that opening of the circuit breaker assembly, which is shown in its closed position in FIG. 1, is accomplished by energizing the solenoid 17. This rotates the latch arm 52 in a counterclockwise direction against the influence of spring 54 to release the latch crank 55. Means (not shown) are provided for automatically de-energizing the solenoid 17 immediately following the opening signal so that the device may be reset quickly in preparation for a reclosing operation. With the latch crank 55 thus released, the opening spring 14 is free to move the stem 38 to the right as viewed in FIG. 1 thereby rotating the element 34 and the bell crank 42 clockwise to open the main interrupting contacts and move the links 40 and 74 vertically upward. This also collapses the latch toggle 62 moving the knee pin 68 and the link 63 downward and to the left to rotate the latch crank 55 and compress the reset spring 59.

As the toggle 62 collapses, the tip of element 67 moves out of the notch 72 so that the reset spring 59 is then free to rotate the latch crank 55 counterclockwise and thereby reset it under the latch tip 60. This also moves the link 63 and the knee pin 68 upward and to the right thereby resetting the toggle 62 in preparation fora relatching operation of the main interrupting contacts 10.

Although not shown for the sake'of brevity, it will be understood by those skilled in the art that the main interrupting contacts 10 will be housed in suitable are extinguishing structure for interrupting any arcs that may be struck between bridging member 30 and the fixed contacts 32 when fault current is interrupted. In addition, the device will also be provided with manual tripping means (not shown) for rotating latch arm 52.

Turning now to the hydraulic components within the head 20 and the housing 22, the high pressure supply system 24 is shown in FIG. 1 to include a hydraulic accumulator 80 supplied by a pump 82 which is coupled to a driving motor (not shown) by a shaft 84. The hydraulic accumulator is divided into a gas filled energy storage chamber 85 and a hydraulic chamber 86 which are separated by a free floating piston 8d. The chamber 86 receives high pressure fluid from the pump 8b to raise the piston 63 and thereby compress the gas in chamber 85. in this manner, energy is stored in chamber 85 so that there will be suificient pressure reserves for several operations should pump failure occur. In the preferred embodiment of the instant invention, the expanded pressure of the gas in chamber 85, when the piston is at its lowest position, is approximately 1400 p.s.i. while a pressure control switch (not shown) connected to chamber 86 is constructed and arranged to turn ofi" the driving motor for pump 82 when the pressure in chamber exceeds 3000' p.s.i. In addition, a relief valve (not shown) is provided to exhaust chamber 86 when the pressure therein exceeds 3400 p.s.i.

High pressure chamber 86 is connected by a conduit 89 to a relay cylinder 9&1 through a relay valve 91 which is urged toward its seat 92 by a spring 94 as well as the pressure in the conduit 89. A second conduit 95 connects the relay cylinder 96 to the upper end of an operating cylinder 96 in which the operating piston 93 is reciprocably disposed and which is mechanically connected to the lower end of link 74. The lower end of cylinder 96 vents to the ambient pressure in the sump 23 through an aper ture 99. The left end of relay cylinder 96, as viewed in FIG. 1, is enlarged for receiving a free floating relay piston 1% having a central bore 161 for slidably receiving the stern 162 of the relay valve @1. The right end of the relay piston 106 is reduced to provide a recess 104 which is connected by a relief port 105 to the sump 23. As a result, when the piston is at the left end of cylinder 96, as seen in FIG. 1, the recess 164 provides a relief path to the sump 23 from the upper end of cylinder 96 and through the conduit 95, the cylinder 9!}, and the relief port 165. p

The flow of high pressure fluid to the relay piston 106 is regulated by a pilot valve 166 and a latch valve 168.- The pilot valve 166 includes a valve member 107 disposed in a lower valve chamber 169 and having conical lower and upper faces 11% and 111 respectively and which is connected by a stem 112 to a reclosing solenoid 114. A spring 116 urges the lower face of the valve element 187 against a lower seat 117 to seal thechamber 109 from an auxiliary supply conduit 118 which is in communication with the main supply conduit 89. An upper pilot valve chamber 119, opening into the lower chamber 109 and having a smaller diameter, is connected by a conduit 120 to a port'121 opening into the lower end of the operating cylinder 96. In addition, a restriction 122 connects conduit 1211 to the chamber 109. The margin- 123 separating the upper and lower chambers 119 and 169 respectively, forms a seat for the upper face 111 of valve element 107.

The latch valve 168 comprises a piston 1-24 disposed in a cylinder 125 and connected at its upper end to the link 56. The upper end of cylinder 125 has a recess 126 which is connected by a relief port 128 to the sump 23. A conduit 130 also places the intermediate portion of cylinder 125 in communication with the chamber 105?. In addition, the lower end of cylinder 125 is connected by a conduit 131 to the left end of the relay cylinder fill. A valve seat 132, consisting of an inwardly extending flange, is disposed in the cylinder 125 between the conduits 13d and 131 and cooperates with a plate-like valve memher 134 carried by a stem 135 extending from the lower end of piston 124. Leakage past piston 104 is shown symbolically by a conduit 136, having a restricted opening 138, and connecting the conduit'131 to relief port 1115.

Operation of the hydraulic control mechanism to effect, reclosing of the main interrupting contacts 16 will now be discussed with reference to 1 16.1. In the preferred embodiment of the invention, the area of the upper seat;

123 is approximately twenty times that of the lower seat 117 so that when the pilot valve 166 is in its closed position, shown in FIG. 1, the source pressure in conduit 118 acts on only a small area of the lower face 118 so that spring 116 is easily able to hold element 107 in this position. When a closing signal energizes solenoid 114, the pilot valve 1% is moved upwardly against the influence of spring 116 until its upper face 111 engages the upper valve seat 123. The source pressure now acts on the entire lower face 110 and only a small area of the upper face 111, the remainder of which is vented to the sump through the large area upper seat 123 and conduit 121 Thus the ele ment 197 is held by the source pressure in a sealed relation against the upper seat 123 in opposition to the downward exertion of spring 116 even after the closing signal to solenoid 114 has closed. It will be appreciated, too, by those skilled in the art that means may also be provided for mechanically moving the element 107 against the upper seat 123 as well as the electrical means just described.

The opening of the pilot valve 1% provides high pressure fluid to the left end of the relay chamber 9@ through conduits 118, 1311 and 131, past the seat 132 and the valve member 134 and through the lower end of the cylinder 125. This drives the relay piston to the right as viewed in FIG. 1 until its reduced portion enters the smaller diameter portion of the cylinder 90 thereby closing the relief port As piston 1616 continues to move toward the right, it picks up the stem 102 of valve 92 and moves it away from its seat 92 and against the influence of spring 94 thereby connecting the cylinder 96 to the high pressure source 86 through conduits 89 and 25. The operating piston 28 is thereby driven toward the lower end of cylinder 96 as the fluid below it exhausts through port 91 Upon this event the links 74 and 411 are moved vertically downward rotating the element 34 and the crank 42 counterclockwise to compress the opening spring 14 and to reclose the main interrupting contacts 111. As the piston 98 nears the lower end of cylinder ?6, a tapered boss 139 on its lower end restricts the flow of fluid from said cylinder to provide smooth deceleration. Thus the piston 23 comes to rest against the cylinder head stop 141) with little or no impact.

While the operating piston 98 is moving toward the lower end of cylinder 96, the pressure on the upper pilot valve surface 111 is held at the ambient value by conduit 129 which opens into the lower portion of cylinder as through port 121 and which, in turn, is in communication with the sump 23 through the relief port 99. When the piston 98 reaches its lowermost position in cylinder 96, however, it closes the port 121 so that the pressure in the upper pilot valve chamber 119 can begin building up through the restriction 122. The spring 116 is then able to reclose the pilot valve 1% against the lower valve seat 117 thereby cutting off pilot pressure to the left side of piston 1% which slowly vents to the sump through the l akage path 13d138. The pressure within cylinder 9% is thereby able to overcome the pressure acting on the left side of piston 1% so that it begins moving toward the left. This allows the spring 94 to close the relay valve 91 and thereby isolate the cylinder 96 from the high pressure source 85. The continued movement of piston Hill to the left then opens chamber 911 into recess 164 so that the pressure on the upper end of chamber 96 can exhaust to the sump 23 through the port 1%. The opening spring 14 is then free to move the stem 38 slightly to the right until the latch toggle element 67 is picked up by the notch '72 in link 74 whereby the mechanism is mechanically latched in closed position.

It will be noted that during the entire closing operation, pilot pressure is acting on the underside of the latch valve piston 124 urging it upwardly. Such upward movement, however, is normally prevented by the engagement of the latch tip 619 by the latch crank 55 since, it will be recalled, crank 55 is normally relatched immediately after an opening operation has commenced. As a result, if a tripping signal is received during any portion of the closing operation just described, solenoid 17 will rotate the latch arm 52- counterclockwise to release the latch crank 55 so that the latch valve piston 124 may be moved upwardly against the reset spring 59 by the pilot fluid pressure acting beneath it. When the lower end of the latch valve piston 124 moves into the recess 126, the chamber will be vented to the sump 23 through the passage This loss of pilot pressure allows the pressure acting on the right end of piston 11%) to drive it to the left whereby relay valve 91 is reclosed and the upper end of chamber as is vented to the sump through the port 1%. The opening spring 14 is then free to drive the partially closed contacts 111 to their fully open position.

it will be recalled from the foregoing discussion that when the operating piston 98 reaches its lowermost position in cylinder 96 during a normal closing operation it will close port 121 to allow the pressure in the upper pilot valve chamber to begin rising so that the pilot valve 106 closes. The pressure beneath the latch valve piston 124 is maintained after pilot valve 126 closes, however, by the pressure in cylinder 9% acting on the right end of piston 11341. This pressure remains until cylinder is vented through port 1% and the latch'link 67 picks up the notch in element '74. As a result, the control 18 is in condition for trip-free operation even when the operating piston 98 is at the end of a switch closing stroke. Thus the latch crank 55 is loaded for rotation in a switch opening direction at any instant that an opening impulse is given either by the pressure beneath the valve piston 124 or by the engagement of link 72 on the latch 67.

When the latch valve piston 124 is released for upward movement under full accumulator pressure within the cylinder 125, the reset spring 59 will be severely compressed. Under normal operating conditions, i.e., with pilot valve 1th? closed, the spring 55? would then drive piston 12% downwardly to reset the latch crank 55 after cylinder 12?- was vented. Consider, however, the action of piston 124 should the pilot valve be held open following a trip free operation. if the valve 134 were not provided, then after the closing of relief port 128 by the downward movement of piston 124, the piston 1111 would begin moving without opposition toward the right, since the cylinder 99 is at sump pressure. Until piston 160 me-t opposition, therefore, there would be a delay in the pressure build-up in cylinder As a result, the force of spring 5? could be suficient to move the piston 124 downward to its latched position during this time delay. With the latch crank 55 thus reset and pilot valve 1116 open, an unwanted reclosure of the circuit breaker would result. Even if the spring pressure were not surficient to relatch crank 55, this delay in pressure build-up within cylinder 125 would cause violent chattering of the mechanism. The Valve 134 is provided to eliminate these undesirable effects.

When the reset spring 59 attempts to relatch the piston 124 while the pilot valve 196 is open, relief port 128 will first be closed and then valve member 134 will begin moving through its valve seat 135. As port 128 is closed the pressure in cylinder 125 will immediately begin rising without regard to the movement of the piston 160 because it will be isolated therefrom by the valve 134. As a result of this pressure build-up the downward movement of piston 124 will be arrested while member 13 is within its seat and before crank 55 can be latched. As long as the pilot valve 106 is open, the piston 124 will be unable to move any further into cylinder 125 so that it cannot be relatched by spring 59 nor can pilot pressure act on piston 1110 to effect a reclosure of the circuit breaker. Relatching of the device can only occur when pilot pressure is removed by a closing of the pilot valve 1'06.

An underpressure valve 144 is provided to prevent the reclosure of the device if the pressure within the cylinder 125 is not sufficient to insure trip-free operation. The underpressure valve 144 includes a piston 145 disposed in a cylinder whose opposite ends are connected to the auxiliary supply conduit M8 and to the relief port 23 respectively. A recess 147 intermediate the ends of cylinder 146 is connected to the conduit 13th which connects the pilot chamber 31% to the cylinder 125. When the pressure within chamber 86, acting on the left end 'of piston 145, is within its desired limits, the piston will be held in an intermediate position against the influence of a spring 143 acting on its other end to block the recess 147. Should the pressure in chamber 86 fall below the desired value, however, spring 14% will move piston 145 to the left in cylinder M6 and connect the relief port 128 to the conduit 13b thereby venting the pilot pressure to the sump so that movement of relay piston ltltl is pre-- vented.

In order to operate the circuit breaker independently of the automatic control just discussed, the maintenance: valve assembly 26 is provided. This assembly includes a valve member d adapted to cooperatively engage a valve seat 151 formed in the conduit 95 between the operating cylinder 96 and the relay cylinder 90. The valve element 15b is mounted on the lower end of an elongate stem 152 which extends through a bore 154 formed in an extension 155 of the block Ztl and which carries a push button 156 on its upper end. A bushing 15? integral with the extension 155 telescopically receives the push button 156 and encases a reset spring 16% circumjacent the upper end of stem 152 and engaging the underside of push button 156 to bias the valve element 15o upwardly and away from the seat 1531.

When the valve lliitl is closed by depressing the push button 156, the circuit breaker may then be operated at a controlled rate of speed by opening a valve 176 in a bypass conduit 178 between the main supply conduit 89 and the cylinder supply conduit 95. By controlling the pressure above piston 98 in this manner, the device may either be closed at a controlled rate of speed or stopped midway between its open and closed position for maintenance purposes. A second valve 177, disposed between bypass conduit 17% and the sump 23, is provided to vent the upper end of cylinder 96 during such maintenance operations.

While only a single embodiment of the instant invention has been shown and described, it is not intended that the invention be limited thereto, but only by the scope of the appended claims.

I claim:

1. A circuit breaker including contact means, contact opening means, fluid pressure operating means for closing said contact means, a source of fluid pressure, pilot means biased toward an initial position and operable when in a'final position to effect the connection of said operating means to said source whereby a contact closing operation will be initiated, actuating means for initiating the'movement of said pilot means toward said final position, pressure means normally being efiective to hold said pilot means in its final position after movement thereto following the operation of said actuating means, said operating means being effective when said contact means reaches its fully closed position to render said pressure rneans 'inetiective to hold said pilot means in its final position so that said pilot means will be biased for return to its initial position.

2. A'circuit breaker including contact means, contact opening means, hydraulic operating means for closing said contact means, a source of hydraulic pressure, pilot means operable when in a first position to effect the conmotion of said operating means to said source whereby said contact means will be moved to its closed position, actuating means for moving said pilot means toward said first position, biasing means urging said pilot means towards a second position, pressure means for holding said pilot means in its first position after movement thereto by said actuating means against the influence of said biasing means, said operating means being efiective when said contact means reaches its fully closed position to render said pressure means inefiective to hold said pilot means in its first position so that said pilot means will be biased for return to its second position by said biasing means and said operating means is disconnected from said source.

3. A circuit breaker including contact means, contact opening means, hydraulic operating means for closing said contact means, a source of hydraulic pressure, pressure responsive pilot means in communication with said source and including an element operable when in a first position to efiect the connection of said operating means to said source whereby said contact means will be moved to its closed position, electroresponsive means for moving said element toward said first position, biasing means urging said element toward a second position, the pressure from said source normally being eliective to hold said element in its first position against the influence of said biasing means, said operating means being effective when it reaches its fully closed position to render said pressure source ineffective to hold said element in its first position so that said element will be returned to its second position by said biasing means and said operating means is disconnected from said source.

4. A circuit breaker including contact means, contact opening means, hydraulic operating means for closing said contact means, a source of hydraulic pressure, a first means including an element operable when in a first position to effect the connection of said operating means to said source whereby said contact means will be moved to its closed position, biasing means urging said element toward a second position, said element having a pair of opposed pressure areas, electroresponsive means for moving said element into its first position, a second means for maintaining a'sufiicient pressure differential between said areas when said element is in its first position so that said element is held in said position against the action of said biasing means, said operating means being effective when it reaches its fully closed position to render said second means ineffective so that the pressure differential between said areas will be insufiicient to hold said element in its second position against said biasing means whereby said operating means is disconnected from said source.

5. A circuit breaker including contact means, contact opening means, hydraulic operating means for closing said contact means, a source of hydraulic pressure, a sump, differential pressure means including an element operable when in a first position to efiect the connection of said operating means to said source whereby said contact means will be moved to its closedposition, means for biasing said element toward a second position, said element having a pair of opposed pressure areas, means for moving said element toward its first position, one of said areas being subjected to the pressure from said source when said element is in its first position, the other of said areas being vented to the sump through said operating means whereby said pressure difference will hold said element in its first position so that said operating means will be connected to said source, a restricted passage interconnecting said pressure areas, said operating means being eifective when it reaches its fully closed position to isolate said other area from the sump so that the pressure between said areas Will be equalized through said restricted passage whereby said element will be returned to its second position by said biasing means.

6. A circuit breaker operating mechanism including biasing means urging said mechanism toward an open position and latch means for holding said mechanism in a closed position in opposition to said biasing means, electro-responsivemeans for releasing said latch means,

hydraulic operating means for closing said mechanism against the action of said biasing means, a source of hydraulic pressure, a sump, a hydraulically operated relay valve for selectively coupling said operating means to said source whereby said mechanism will be moved to its closed position, a pilot valve connected to said source and including an element having pressure areas on both sides thereof, said element having an initial position which separates said relay valve from said source, means biasing said element toward said initial position, means for moving said element out of its initial postion, one of said areas being subjected to the pressure from said source when said element is out of its first position, a relief port venting the other of said areas to the sump whereby said pressure difierence will hold said element away from its initial position so that said relay valve is connected to said source, a restricted passage interconnecting said areas, said operating means being operative to close said relief port when said mechanism reaches its fully closed position thereby isolating said other area from the sump so that pressure between said elements may be equalized through said restriction whereby said element will be returned to its initial position.

7. A circuit breaker operating mechanism including contact means, contact opening means, hydraulic operating means for closing said contact means, a source of hydraulic pressure, a first conduit for connecting said operating means to said source, hydraulically operated relay means including a normally closed valve in said first conduit means for isolating said operating means from said source, a second conduit connecting said relay means to said source, a pilot valve disposed in said second conduit means and having a pair of opposed pressure faces, a chamber for said pilot valve disposed in said second conduit means and having a relatively small inlet, an outlet and a relatively large venting aperture, biasing means urging said relay valve toward a first position wherein one of said faces is against said inlet to separate said relay means from said source, a pressure relief port connected to said venting aperture, means for moving said pilot valve to a final position to connect said relay means to said source to initiate a switch closing operation, movement of the pilot valve to its final position moving said other face against said venting aperture so that the entire area of said one face is exposed to said source and the other face is vented through said pressure relief port, whereby the pressure difierence on said faces will hold said pilot valve in its final position, a restricted passage connecting said venting aperture to said chamber around said other face, said operating means being operative when said contact means reach their fully closed position to close said pressure relief port so that the pressure between said faces may be equalized through said restricted passage whereby said pilot valve will be returned to its initial position.

8. A circuit breaker operating mechanism including contact means, fluid pressure operating means for closing said contact means, a source of fluid pressure, a first pressure responsive means operable to connect said operating means to said source whereby said contact means are closed, a second pressure responsive means, selectively operable pilot means for effecting the connection of said first and second pressure responsive means to said source to initiate a closing operation of said contact means, said second pressure responsive means being operable from a closed position to an open position to elfect the venting of said operating means to interrupt the closing of said contact means, latch means for bolding said second pressure responsive means in its closed position against said source pressure, selectively operable latch releasemeans, biasing means urging said second pressure responsive means toward its closed position, and normally open auxiliary valve means operable to isolate said first pressure responsive means from said source when said pilot means remains open after the release of said second pressure responsive means has initiated the venting of said operating means.

9. A circuit breaker operating mechanism including contact means, fluid pressure operating means for closing said contact means, a source of fluid pressure, a first pressure responsive means operable to connect said operating means to said source whereby said contact means are closed, a second pressure responsive means, selectively operable pilot means for eltecting the connection of said first and second pressure responsive means to said source to initiate a closing operation of said contact means, said second pressure responsive means being operable from a closed position to an open position to vent said first pressure responsive means and interrupt the closing of said contact means, latch means for holding said second pressure responsive means in its closed position against said source pressure, selectively operable latch release means for releasing said second pressure responsive means for movement to its open position by-said source pres sure, biasing means urging said second pressure responsive means toward its closed position but normally being ineffective to relatch the same against said system pressure when said pilot means is open, and normally open auxiliary valve means associated with said second pressure responsive means and operable to isolate said first pressure responsive means from said source when said pilot means remains open after said second pressure responsive means has been unlatched to vent said first pressure responsive means.

10. A circuit breaker operating mechanism including contact means, hydraulic operating means for closing said contact means, a source of hydraulic pressure, conduit means interconnecting said operating means and said source, a first pressure responsive means including valve means disposed in said conduit means and being a normally closed position for isolating said operating means from said source, selectively operable pilot means for effecting the connection of said first pressure responsive means to said source so that said valve means is opened, pressure relief means associated with said first pressure responsive means, a second pressure responsive means in communication with said first pressure responsive means and having a normal position which isolates said first pressure responsive means for said pressure relief means, said source pressure urging said second pressure responsive means away from said normal position to vent said first pressure responsive means, latch means for holding said second pressure responsive means in its normal position, biasing means urging said second pressure responsive means toward its normal position but being ineffective to relatch said second pressure responsive means against said source pressure, latch release means, auxiliary valve means operable by said second pressure responsive means to isolate said first pressure responsive valve means from said source when said pilot means remains in its open position to prevent the relatching of said second pressure responsive valve means.

11. A circuit breaker operating mechanism including contact means, contact opening means, restraining means for holding said contact means in a closed position in opposition to said opening means, electroresponsive trip means for releasing said restraining means, hydraulic operating means for closing said contact means, a source of hydraulic pressure, conduit means interconnecting said operating means and said source, a first pressure responsive means including valve means disposed in said conduit means and being in a normally closed position for isolating said operating means from said source. selectively operable pilot means for effecting the connection of said first pressure responsive means to said source so that said valve means is opened, a relief port associated with said first pressure responsive means, a second pressure responsive valve means in communication with said first pressure responsive valve means and having a normal position which closes said port, said source pressure urging said second pressure responsive means away from said normal position to vent said first pressure responsive means, and latch means connected to said restraining means for bolding said second pressure responsive means in its normal position, biasing means urging said second pressure responsive means toward its normal position but being ineffective to relatch the same against said source pressure, said second pressure responsive means including auxiliary valve means operable to isolate said first pressure responsive valve means from said source when said pilot means remains in its open position to prevent the relatching of said second pressure responsive valve means.

12. A circuit breaker operating mechanism including contact means, contact opening means, restraining means for holding said contact means in a closed position in opposition to said opening means, trip means for releasing said restraining means, hydraulic operating means for closing said contact means, a source of hydraulic pressure, a first conduit means interconnecting said operating means and said source, a first pressure responsive relay means including a relay valve disposed in said conduit means and being in a normally closed position for isolating said operating means from said source, a second con duit means connecting said pressure responsive relay means to said source, a selectively operable pilot valve disposed in said second conduit means and actuable to connect said first pressure responsive means to said source so that said relay valve is opened, a pressure relief port in communication with said first pressure responsive means, a second pressure responsive valve means in communication with said first pressure responsive valve means and having a normal position which closes said port, said source pressure urging said second pressure responsive means away from said normal position to vent said first pressure responsive relay means and close said relay valve, latch means connected to said restraining means for bolding said second pressure responsive means in its normal position, biasing means urging said second pressure responsive means toward its normal position but being ineffective to relatch said second pressure responsive means against said source pressure, said second pressure responsive means including auxiliary valve means in said second conduit means and having a normally open position when said second pressure responsive means is latched, said auxiiiary valve means being in a closed position to isolate said first pressure responsive valve means from said source if said pilot valve means remains open to prevent the re latching or" said second pressure responsive valve means.

13. A circuit breaker including contact means, contact opening means, pressure responsive operating means for closing said contact means, a source of pressure, pilot means having an operative position for effecting the connection of said operating means to said source whereby a contact closing operation will be initiated, actuating for moving said pilot means to its operative position, said pilot means normally being held in said operative position after movement thereto following the operation of said actuating means, and means operative when said contact means reaches its fully closed position to effect the release of said pilot means for movement out of its operative position.

14. A circuit breaker operating mechanism including contact means, a source of pressure, a first pressure responsive means operative to effect the closure or said contact means, a second pressure responsive means, selectively operable pilot means having an operative position for effecting; the connection of said first and second pressure responsive means to said source to initiate a closing operation of said contact means, said second pressure responsive means having an operative positionfor venting said first pressure responsive means and thereby interrupting the closure of said contact means, means for holding said second pressure responsive means in an unoperative position, selectively operable release means for releasing said last-mentioned means so that said second pressure responsive means may move to its operative position under the influence of said pressure, and normally open valve means operable to isolate said first pressure responsive means from said pressure source if said pilot means remains in its operative position after the release of said second pressure responsive means has initiated the venting of said first pressure responsive means.

References @ited in the file of this patent UNlTED STATES PATENTS 2,631,190 Umplirey Mar. 1c, 1953 2,658,969 Umphrey Nov. 1%, 1953 2,662,134 Umphrey -4 Dec. 8, 1953 

1. A CIRCUIT BREAKER INCLUDING CONTACT MEANS, CONTACT OPENING MEANS, FLUID PRESSURE OPERATING MEANS FOR CLOSING SAID CONTACT MEANS, A SOURCE OF FLUID PRESSURE, PILOT MEANS BIASED TOWARD AN INITIAL POSITION AND OPERABLE WHEN IN A FINAL POSITION TO EFFECT THE CONNECTION OF SAID OPERATING MEANS TO SAID SOURCE WHEREBY A CONTACT CLOSING OPERATION WILL BE INITIATED, ACTUATING MEANS FOR INITIATING THE MOVEMENT OF SAID PILOT MEANS TOWARD SAID FINAL POSITION, PRESSURE MEANS NORMALLY BEING EFFECTIVE TO HOLD SAID PILOT MEANS IN ITS FINAL POSITION AFTER MOVEMENT THERETO FOLLOWING THE OPERATION OF SAID ACTUATING MEANS, SAID OPERATING MEANS BEING EFFECTIVE WHEN SAID CONTACT MEANS REACHES ITS FULLY CLOSED POSITION TO RENDER SAID PRESSURE MEANS INEFFECTIVE TO HOLD SAID PILOT MEANS IN ITS FINAL POSITION SO THAT SAID PILOT MEANS WILL BE BIASED FOR RETURN TO ITS INITIAL POSITION. 